Oxalic acid, namely oxalic acid, is one of the simplest organic binary acids. It is usually a colorless transparent crystal, which plays an important role in industry. Oxalic acid can remove rust. Oxalic acid is ubiquitous in nature. Oxalate is often found in the cell membranes of plants such as Funiuhua, Leymus chinensis, Oxalis and Rumex rubra. Almost all plants contain oxalate.

The simplest resolution method is that oxalic acid itself can be made into white powder and dissolved in water to form an aqueous solution. Industrial hydrochloric acid, which contains impurities and appears mostly as yellow-green liquid, will produce white acid fog when exposed to air. There was once a leakage of containers filled with acid on the construction site, which resulted in a shallow pit in the cement air in a few hours. So if possible, try not to purchase this acid, because too corrosive will destroy the cement in the joint. It may affect the quality of external perception, but it may cause water seepage at the joint. Or the site buys oxalic acid back from the chemical shop to make water solution safer to use. But the most important thing is to strengthen the supervision of workers.

Industrial production method of oxalic acid

1. Carbon monoxide purified by sodium formate reacts with sodium hydroxide under pressure to produce sodium formate, which is then dehydrogenated at high temperature to produce sodium oxalate. The waste oxalic acid is obtained by lead (or calcification), acidification, crystallization and dehydration of sodium oxalate. The synthesis pressure of carbon monoxide and sodium hydroxide is generally 1.8-2.0 MPa. The dehydrogenation temperature is 400 C.

2. Oxalic acid was synthesized by oxidation of starch or mother liquor of glucose with nitric acid-sulfuric acid in the presence of alum catalyst. Nitrogen oxide in waste gas is recycled to form dilute nitric acid in the absorption tower.

3. Ethylene glycol oxidation is obtained from ethylene glycol by air oxidation in the presence of nitric acid and sulfuric acid.

4. The oxidation of propylene was stopped in two steps. In the first step, propylene is oxidized by nitric acid to form a-nitrolactic acid, and then oxalic acid is obtained by further catalytic oxidation. In the second step, mixed acid can also be used as oxidant. Propylene oxidation process consumes industrial-grade oxalic acid dihydrate, the total yield of propylene is more than 90%.

5. Carbonyl synthesis of carbon monoxide after purification to more than 90%, in the presence of palladium catalyst and butanol carbonylation reaction, the formation of dibutyl oxalate, and then hydrolysis to oxalic acid, this method is divided into liquid phase method and gas phase method, the gas phase reaction conditions are low, the reaction pressure is 300-400 kPa. The liquid phase reaction pressure is 13.0-15.0 MPa.